The war between teens and authority figures has a new  or old  front: ears.
British shopkeepers tired of teenage loiterers have turned to the Mosquito teen
repellent, which emits a high-pitch frequency that most teenagers can hear  but
not most adults.

But now teens have struck back against the Mosquito: They are using the same
sound to communicate without adults' knowledge.

At issue is a text-message ringtone that emits the same pitch as the Mosquito.
Using it, students can learn about a new message while they're in class  where
they're not supposed to be using their cellphones. Most of their teachers can't
hear the alert.

Inventor Howard Stapleton, creator of the Mosquito teen repellent, says only a
few people over age 30 can hear the Mosquito's sound. He and his 16-year-old
daughter Isabel talk to Melissa Block about the sound, which has been dubbed
"Teen Buzz."